CA2071888A1 - Ceria electrolyte composition - Google Patents
Ceria electrolyte compositionInfo
- Publication number
- CA2071888A1 CA2071888A1 CA002071888A CA2071888A CA2071888A1 CA 2071888 A1 CA2071888 A1 CA 2071888A1 CA 002071888 A CA002071888 A CA 002071888A CA 2071888 A CA2071888 A CA 2071888A CA 2071888 A1 CA2071888 A1 CA 2071888A1
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- CA
- Canada
- Prior art keywords
- composition
- chosen
- group
- electrolyte
- fuel cell
- Prior art date
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Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M8/00—Fuel cells; Manufacture thereof
- H01M8/10—Fuel cells with solid electrolytes
- H01M8/12—Fuel cells with solid electrolytes operating at high temperature, e.g. with stabilised ZrO2 electrolyte
- H01M8/124—Fuel cells with solid electrolytes operating at high temperature, e.g. with stabilised ZrO2 electrolyte characterised by the process of manufacturing or by the material of the electrolyte
- H01M8/1246—Fuel cells with solid electrolytes operating at high temperature, e.g. with stabilised ZrO2 electrolyte characterised by the process of manufacturing or by the material of the electrolyte the electrolyte consisting of oxides
- H01M8/126—Fuel cells with solid electrolytes operating at high temperature, e.g. with stabilised ZrO2 electrolyte characterised by the process of manufacturing or by the material of the electrolyte the electrolyte consisting of oxides the electrolyte containing cerium oxide
-
- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
- C04B35/50—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on rare-earth compounds
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/30—Hydrogen technology
- Y02E60/50—Fuel cells
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
- Y02P70/50—Manufacturing or production processes characterised by the final manufactured product
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- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Manufacturing & Machinery (AREA)
- Ceramic Engineering (AREA)
- General Chemical & Material Sciences (AREA)
- Sustainable Energy (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- Sustainable Development (AREA)
- Life Sciences & Earth Sciences (AREA)
- Materials Engineering (AREA)
- Structural Engineering (AREA)
- Organic Chemistry (AREA)
- Fuel Cell (AREA)
- Conductive Materials (AREA)
- Compounds Of Alkaline-Earth Elements, Aluminum Or Rare-Earth Metals (AREA)
Abstract
A ceria electrolyte composition is disclosed. The composition provides high ionic conductivity and low electronic conduc-tivity under reducing conditions. Fuel cells employing the disclosed composition exhibit improved efficiency and power density.
Description
2U71~88 -- . .
Description Ceria Electrolyte Composition Technical Field This invention relates to solid electrolyte fuel cells and electrolytic cells and more particularly, to electrolyte compositions for use in solid electrolyte fuel cells and electrolytic cells. , 8ackground of the Invention A fuel cell is a device for directly converting the chemical energy of the fuel into electrical power.
A fuel cell comprises an anode, a cathode, and an electrolyte disposed between the two electrodes.
In the operation of a ~ypical fuel cell, fuel gas is fed to a porous anode and an oxidant gas is fed to a porous cathode. The reactant gases diffuse through the electrodes and electrochemically react to yield water, heat, and electrical energy. At the anode, the fuel gives up electrons in an electrochemical oxidation reaction. The electrical current so generated is conducted from the anode through an external circuit to the cathode. At the cathode, the ; electrons are electrochemically combined with the oxidant. A flow of ions through the electrolyte completes the circuit.
~ 25 Fuel cells may be categorized according to the ;~ type of electrolyte used. Four types of fuel cells t , . ~
.t , .
SUeSTlTUlE Sl~E~
~ ., . . ~ ... , . .. . . . . . ,, . , . . . .. - . . . .
207~'~88 WO9l/09430 PCT/US90/07075 : - 2 are generally considered to be in the mainstream of the technology: alkaline fuel cells, acid fuel cells, molten carbonate fuel cells and solid electrolyte fuel cells.
Solid electrolyte fuel cells operate at high temperature and allow direct consumption of hydrocarbon fuels to provide a high power density~
Solid electrolyte fuel cells also eliminate liquid electrolyte containment pro~lems.
The use of ceria compositions as the electrolyte in solid electrolyte fuel cells is known, see, e.g., Tuller, H.L. and Nowick, A.S., "Doped Ceria as a Solid Oxide Electrolyte", JournaI of the Electrochemical Society: Solid-State science, Volume 122, No. 2,225 (February 1975). A ceria electrolyte offers a high ionic conductivity at temperatures in the range of 600 to 1000'C. However, in a reducing atmosphere such as that encountered on the hydrogen electrode side of the electrolyte, a conventional ceria electrolyte becomes an electronic as well as an ionic conductor, and allows short circuiting across the electrolyte. The short circuiting reduces the performance of the fuel cell.
What is needed in the art is a way to eliminate or reduce these losses so that ceria electrolyte compositions may find practical application in fuel cell power plants.
Disclosure of the Invention An electrolyte composition is disclosed. The composition comprises:
CexMyDz2-d ' SU~STITUTE SUET
,.. . .. , .. , ~ . . . . / . . ~ ... ~ . . . .. .. . . . . . ..
2071~
PCr/US90~07075 wherein:
m is a primary dopant chosen from the group consisting of Pr,Nd,Pm,Sm,Eu,Gd,Tb,Dy,Ho,Er,Tm,Yb, Lu,Sc,Y,La and Ca D is a secondary dopant chosen from the group consisting of Pr,Sm,Eu,Tb,Fe,Co and Ni, M ~ D, M is present in an amount mole fraction y, sufficient to increase the ionic conductivity of the composition, D is present in an amount, mole fraction z, sufficient to decrease the electronic conductivity of the composition under reducing conditions, and about .
o.oS < d < about 0.30.
The composition of the present invention provides high ionic conductivity and low electronic conductivity under reducing conditions.
A fuel cell is disclosed. The ~uel cell . comprises an anode, a cathode, and a solid electrolyte .
: 20 between the anode and cathode, wherein the solid electrolyte comprises the composition described above.
A process for generating electricity is also disclosed. The process comprises providing a fuel cell, wherein the fuel cell comprises the fuel cell described above, supplying a fuel to the anode of the . fuel-cell, supplying an oxidant to the cathode side of the fuel cell, and electrochemically reacting the fuel - and the oxidant to prov.ide an electrical current.
....
.~ Brief Description of the Drawings ;- -~30 Figure:1 shows a.cross-sectional view of-a-fuel -,cell.. of *he;present invention~
.Figure 2.shows a plot of:log-total conductivity . as a function of oxygen partial pressure;
~! .
2071~88 WO9lt09430 PCr/US90/07075 ~:
Figure 3 shows a plot of electronic conductivity vs. secondary dopant level for a number of electrolyte compositions;
Figure 4 shows a plot of electrolytic domain boundary vs. secondary dopant level for a number of electrolyte compositions;
Figure S shows a plot of fuel cell voltage and electronic short circuit current vs. current density for two electrolyte compositions;
Figure 6 shows a plot of cell efficiency and power density vs. current density for two electrolyte compositions.
Description of the Preferred Embodiment ;~
The ceria electrolyte composition of the prasent invention comprises:
X y Z02-wherein:
M is a primary dopant chosen from the group consisting of Pr,Nd,Pm,Sm,Eu,Gd,Tb,Dy,Ho, Er,Tm,Yb,Lu,Sc,Y,La and Ca, D is a secondary dopant chosen from the group consisting of Pr,Sm,Eu,Tb,Fe,Co and Ni, M ~ D, and x, y, z and 2-d are coefficients denoting the atomic fractions-of the respective components and fall within the ranges set out below.
The primary dopant is chosen-to increase the ionic conductivity of the electrolyte relative to ceria compositions lacking the primary dopant.
Suitable primary dopants are-known~in the~art.
Preferably, the primary dopant, M,-is chosen from-the group co~sisting of Gd, Y, Ca, Sm, La, Nd and Sc.
More pr~ferably, M comprises Gd, Sm, Ca or Y. Most preferably, ~ comprises Gd.
SUBSTITUIE SHEE~
..~ , . .. . . .
, . ~., . .. ; ~ .. . .
207 1~8~
The secondary dopant, D, is chosen to decrease the electronic conductivity of the electrolyte composition under reducing conditions, relative to the electronic conductivity of ceria compositions lacking the secondary dopant. Suitable secondary dopants, D, comprise elements which reduce more easily than Ce.
Preferably, the secondary dopant has an ionic radius similar to that of Ce. Most preferably, D comprises Pr or Sm.
Specific examples of the composition of the present invention include:
cexGdyprzo2-dl CexGdysmzo2-d ' CexGdyEuzo2-d ' CexGdyTbzo2-d ~ ' .
cexGdyFez02-d ' CexGdycozo2-d ' CexGdyNizo2-d ' cexYyPrz02_ CexYySmz02 d~
CexYyEUz02_d ~ -- -. . . . ..
cexyyTbzo2-d ~ ., cexyyFezo2-d ' SUBSTITUTE SHET
.. , , ., , .. , , " . . . . . .. . . . . . .... . ....
.. ... .. . ... ..
. .
, , . ~, . ` -. ` , . . . .
.
i . , , ~ . ~ ` . . ` . . . .
- ........ ~ .. . . . . . .. . .
~071:~`8 W091~09430 PCT/US90/0707~ .
CexYycozo2-dl CexYyNiz02 d' CexCayPrzo2-d ' , Cexca 5CexCayEuzo2-dl ; x y z 2-d' ;
Ce Ca Fe o excaycz2-d ~ , ,, .
'i' .:
10Cexsmyprzo2-d : CexSmyEUz2_dl cexsmy~bzo2-d ' myFezo2 d' .~ Ce Sm Co d' ~; 15~ and CexSmyNizO2 d wherein x,y,z and d are within the ranges set out below.
: : The atomic fraction of Ce,. x, is within the range of about 0.7 to about O.9 and preferably falls within the range of about 0.75 to about 0.85.
The atomic fractions of the primary dopant, y, and the atomic fraction of the secondary dopant, z, are~chosen to the maximize ionic conductance of the SU8S~I~UTE SHE~
" .. . " . . ; . . , ;. .. ... .. . - . ;, ,.. .. ,. . -, . . . . . .
:.!,, . . .. . '. . " , :,', .,-,' ',' ", ,, . ,. ,'.. '.. ' ' . ' . ' ' 2071~8~
WO9t/09430 electrolyte and minimize the electronic conductance of the electrolyte under reducing conditions. The atomic fraction of primary dopant in the present composition, :
y, is preferably within the range of about 0.1 to about 0.3 and most preferably falls within the range from about 0.15 to about 0.25. The atomic fraction of secondary dopant in the present composition, z, is preferably within the range of about 0.001 to about 0.1 and most preferably falls within the range of about 0.01 to about 0.05. -~
The atomic fraction of oxygen in the present composition, 2-d, varies with the oxidation states of the primary and secondary dopants, with atomic fractions y and z and with oxygen partial pressure.
An oxygen vacancy is formed for each divalent dopant atom, one half of an oxygen vacancy is formed or each trivalent dopant atom and no o~ygen vacancy is formed for each quàdravalent dopant atom. The atomic fraction of oxygen in the composition of the present invention typically ranges from about 1.7 to ~bout 1.95 and most typically ranges from about 1.89S to about 1.9. Values for d may therefore typically range from 0.05 to about 0.30 and most typically range from 0.1 t~ 0.105.
The ceria electrolyte of the present invention may be made by conventional solid.state techniques.
.Inorganic precursor..materials are mixed and reacted to form a product of the desired composition. Precursor materials comprise compounds which decompose under suitable conditions to yield reactants which are then ' reacted to form the ceria.electrolyte.:product. The : relative amount of each precursor material in`the mixture is chosen to provide a-product ha~ing th~-desired ~olar composition.
~ 35 In a preferred process, stoichiometric amounts of water soluble inorganic precursor materials are UIE SH~I ' .
-. , . --- . -- - - - . ........ ... . . . - . .
. ~ . . . .
207~88 -PCI`/US90/0707s ':
combined to form an aqueous solution. Reactants are .
precipitated from the solution. The precipitate is filtered, dried and ground to form a fine powder. The ~;
powder is then calcined in air. The calcined powder is pressed and sintered to form the ceria electrolyte ;-composition.
The ceria electrolyte of the present invention is used as the electrolyte in a solid electrolyte fuel cell. A solid electrolyte fuel cell of the present invention is shown in Figure l and comprises an anode 2, a cathode 4 and a ceria electrolyte 6 of the -present invention between the anode 2 and cathode 4, an external circuit 8 electrically conne~ting the anode 2 and the cathode 4, a first flow field 10 having passages 12 for directing reactants to and reaction products away from the anode 2, and a second flow field 14 having passages 16 for directing reactants to and reaction products from the cathode 4.
The fuel cell is operated at pressures between 1 and 10 atm and temperatures between 600-C - lOOO-C to generate an electrical current by electrochemically reacting the fuel and oxidant streams. Key fuel cell performance parameters include current density, cell voltage, and power density and cell efficiency.
Current density is defined as the current generated per-unit cross sectional area of the electrolyte expressed in milliamps/square centimeter (mA/cm2). Cell voltage is defined as the voltage generated by the cell expressed in volts--(V)-. Power density is defined as the power generated per unit-cross sectional area of the~electrolyte,~ expressed as - watts/square centimeter (w/cm2). Cell efficiency is defined as DC power produced/standard enthalpy of fuel electrochemically converted. ~-The electrolyte composition of the present invention provides high ionic conductance but exhibits SUt~ST~TUTE SHE~T
..... . ... ... . ... . . . .... . ..... .. .. .. ... . .. . ... . . .. . ... .
.,.. ,... : . . . - . : , .. , ~ .
.
- . .
- -' ' ' .
, ~ . ' , ~ , .
2071888 ::
PCI`/US90/0707s g _ .-low electronic conductivity at low 2 partial pressures. Preferably, the electrolyte of the present invention exhibits an electrolytic conductivity of less than about 0.3 S/cm at an 2 partial pressure of about 1 X 10 23 atm. The behavior of the electrode of the present invention with regard to 0 2 partial pressure may be characterized by reference to an electrolytic domain boundary value. The electrolytic domain boundary is defined as the 2 partial pressure at which the electronic conductivity of the electrolyte equals the ionic conductivity of the electrolyte. Preferably, the electrolyte of the present invention exhibits an electrolytic domain boundary of less than about 5 X 10 19 atm 2 at 700 C.
Most preferably, the electrolyte of the present invention exhibits an electrolytic domain boundary of ;
less than about 5 X 10 20 atm 2 at 700C. T~e low electrolytic domain boundary of the electrolyte provides performance advantages to fuel cells in which the electrolyte is employed. Since the electrolyte of the present invention provides low electronic conductivity and high ionic conductivity at low 2 partial pressures, short circuiting across the electrolyte is reduced. Power and efficiency losses which result from short circuiting are correspondingly reduced.
The basis for the electronic conductivity of a conve~tional ceria electrolyte appears to be a -`
departure from stoichiome~ry in the ceria as it is reduced under low 2 partial pressures.
The reaction may-be expressed as~
oO - VO ~ 2e + 1/2 2(gas)~' ~~
where~
" .. . . . . . . . .
0O is an oxygen site in the ceria electrolyte, ~! 35 and ,, .
",.
SU~STITllTE SHEET
- ' . " ' ' ' . ~ . ' . ' ' ' ' .
2~71~88 ~
W091/Og430 PC~/~S90/07075 V0 is a vacant positively charged site in the ceria electrolyte.
Reduction converts an oxygen to a vacant site plus two free electrons. Movement of the free electrons through the electrolyte provides the mechanism for internal short circuiting of the electrolyte.
While not wishing to be bound by any particular theory, it is believed that the secondary dopant, D, ;
of the composition of the present invention minimizes the electronic conductivity of the composition by trapping electrons, i.e. by reducing the net total of mobile electrons in the composition.
52.11 grams Ce(N03)3 6H20, 10.56 grams Gd(N03)2 and 0.65 grams Pr(N03) were combined, dissolved in distilled water and diluted to form a 0.3M nitrate solution. The nitrate solution was added dropwise to a bath o~ 0.3M ammonium oxalate to precipitate the Ce, Gd and Pr reactants. Additions of 10~ N~40H were made to maintain the pH between 6.5 and 7Ø After all the nitrate solution had been added to the bath, additional NH40H is added to raise the pH of the solution to 7.5 to ensure complete precipitation. The precipitate was filtered, oven dried at 140-C and crushed in a porcelain mortar and pestle to form a fine powder. The powder was calcined in an alumina crucible-in air at 750-C for 16 hours. The calcined powder was mixed with 0.3 wt % polyvinyl alcohol as a binder. The mixture was pressed at 200MPa, crushed, reground and finally repressed at 400MPa to form wafers. The wafers were sintered at temperatures ~etween 1300-C and 1525-~ to form wafers having a nominal composition of CeO ~Gdo 19PrO 012 d SUBSTITUTE SHEET
.. i.......... . . . ~......... ~ . . .
. . .
~ . . . . . . .. . . . . .
; ~ , . - - . .
. . . -. , ., ~ , . .
2`07~88 Wafers havi~g a nominal composition:
ceO 8Gdo~ 22-d were also prepared by a process analogous to the : ;
process described above.
Conductivity measurements were made using the A.C. impedence technique. Figure 2 shows total -~
conductivity (S/cm) of each composition as a function.
f 2 partial pressure (atm) at 700C. The electrolytic domain boundary of the CeO 8Gdo 2l 9 composition was about 8 X 10 19 atm 2' The electrolytic domain boundary of the 0.8 0.lsPro.olo2-d composition was 4.6 X 1o~
atm 2' Wafers having nominal compositions:
ceO.8GdO.2_zPrz02_d and ceO 8Gdo2-zSmz2-d where: 0 < z < 0.06 and 0.07 < d < 0.1 , were prepared by processes analogous to the process described in Example 1.
Figure 3 shows a plot of electronic conductivity under reducing conditions (Po2 = 1 x 10 23 atm) versus atomic ;fraction of secondary dopant for the above described wafers at 700C-. ; . .
With regard to the CeO 8Gdo 2_zPrz02_ compositions, the electronic conductivity reaches a , . . ,; . .. .. . ... ..... . . . . . .
minimum of about 0.18 S/cm at a mole fraction Pr of about 0.010. The results obtained using Sm as a ~;
` SUBSTITU~E SHEI
2071~8 WO91/09430 PCT/US90/07075 `
secondary dopant were in agreement with those obtained ;
using Pr as the secondary dopant.
Figure 4 shows a plot of electronic domain boundary (atm 2) vexsus atomic fraction of secondary ,' 5 dopant for the above described wafers at 700-C. The electronic domain boundary of the Ce~ 8Gd2 XPrx02 d compositions, fell below about 5XlO atm for atomic fractions of Pr of greater than about 0.001. The results obtained using Sm as the secondary dopant were in agreement with those using Pr as the secondary dopant.
The conductivity data collected in Example I were used to calculate the performance of fuel cells using each of the electrolyte compositions. The calculations were based on a fuel cell having a 0.005 inch thick electrolyte layer operated at 710'C with negligible electrode losses. The method of calculation is conventional in the art, e.g. see generally, P.N. Ross, Jr. and T . G . Benjamin, "Thermal Efficiency of Solid Electrolyte Fuel Cells with Mixed Conduction", Journal of Power Sources 1 (1976/77) 311-321.
Figure 5 shows a plot of calculated cell voltage and calculated electronic short circuit current versus current density`-at 710-C. A fuel cell having an electrolyte of the present invention exhibits an 'electronic short circuit current that is substantially lower than the short circuit current exhibited by fuel cell ha~ing a CeO BGdo 22-d ëlectrolyte at current densities l~ss than 2000 ma/cm . '' Figure 6 shows a plot`'of calculatéd celi efficiency and-calculated power density versus current density at'710-C. A fuel cell having an electrolyte composition of the present invention exhibits a maximum cell efficiency of about 0.48 at a SUBSTITUTE SHET
... , . . . . . , . . , , . . .. ., ., ,, . .. , ~ . ., . , .. , . ",, . .,,,,, . ,,, . , .. , . .. ~ . .. .. ... . . . . .. .. .....
~ ' ' , ' ,, ' ., , : , ' ,' ' ,, ~ 1~ , ,~, ' ' . , 2 0 7 ~
WOgl/09430 PCT/US90/07075 current density of about 750A/cm2, while a cell having a CeO 8Gdo 22 d electrolyte exhibits a maximum cell efficiency of about 0.4 at a current density of about 1000 mA/cm2.
A fuel cell having an electrolyte of the present invention exhibits a maximum power density of about 1.2 w/cm2 at a current density of about 2400 mA/cm2 at 710-C, while a fuel cell having CeO 8Gdo 22 d electrolyte exhibits a maximum power density of about 0.9 w/cm2 at a current density of about 2000 mA/cm2 at 710-C.
The electrolyte composition of the present invention provides high ionic conductivity and reduced electronic conductivity under low oxygen partial pressures. Fuel cells employing the electrolyte composition of the present invention will exhibit improved efficiency and higher power density relative to fuel cells employing conventional ceria electrolyte compositions, due to a reduction in hort circuiting between the electrodes of the fuel cell.
While preferred embodiments have been shown and described, various modifications and substitutions may be made thereto without departing from the spirit and scope of the invention. Accordingly, it is to be understood that the present invention has been described by way of illustrations and not limitation.
What is claimed is:
,. .. ..
, ~ - SU5STITUTE SHET
.,.. , ' ~ , . ~.
., :
~ ' : ' . ' ;~\
.
Description Ceria Electrolyte Composition Technical Field This invention relates to solid electrolyte fuel cells and electrolytic cells and more particularly, to electrolyte compositions for use in solid electrolyte fuel cells and electrolytic cells. , 8ackground of the Invention A fuel cell is a device for directly converting the chemical energy of the fuel into electrical power.
A fuel cell comprises an anode, a cathode, and an electrolyte disposed between the two electrodes.
In the operation of a ~ypical fuel cell, fuel gas is fed to a porous anode and an oxidant gas is fed to a porous cathode. The reactant gases diffuse through the electrodes and electrochemically react to yield water, heat, and electrical energy. At the anode, the fuel gives up electrons in an electrochemical oxidation reaction. The electrical current so generated is conducted from the anode through an external circuit to the cathode. At the cathode, the ; electrons are electrochemically combined with the oxidant. A flow of ions through the electrolyte completes the circuit.
~ 25 Fuel cells may be categorized according to the ;~ type of electrolyte used. Four types of fuel cells t , . ~
.t , .
SUeSTlTUlE Sl~E~
~ ., . . ~ ... , . .. . . . . . ,, . , . . . .. - . . . .
207~'~88 WO9l/09430 PCT/US90/07075 : - 2 are generally considered to be in the mainstream of the technology: alkaline fuel cells, acid fuel cells, molten carbonate fuel cells and solid electrolyte fuel cells.
Solid electrolyte fuel cells operate at high temperature and allow direct consumption of hydrocarbon fuels to provide a high power density~
Solid electrolyte fuel cells also eliminate liquid electrolyte containment pro~lems.
The use of ceria compositions as the electrolyte in solid electrolyte fuel cells is known, see, e.g., Tuller, H.L. and Nowick, A.S., "Doped Ceria as a Solid Oxide Electrolyte", JournaI of the Electrochemical Society: Solid-State science, Volume 122, No. 2,225 (February 1975). A ceria electrolyte offers a high ionic conductivity at temperatures in the range of 600 to 1000'C. However, in a reducing atmosphere such as that encountered on the hydrogen electrode side of the electrolyte, a conventional ceria electrolyte becomes an electronic as well as an ionic conductor, and allows short circuiting across the electrolyte. The short circuiting reduces the performance of the fuel cell.
What is needed in the art is a way to eliminate or reduce these losses so that ceria electrolyte compositions may find practical application in fuel cell power plants.
Disclosure of the Invention An electrolyte composition is disclosed. The composition comprises:
CexMyDz2-d ' SU~STITUTE SUET
,.. . .. , .. , ~ . . . . / . . ~ ... ~ . . . .. .. . . . . . ..
2071~
PCr/US90~07075 wherein:
m is a primary dopant chosen from the group consisting of Pr,Nd,Pm,Sm,Eu,Gd,Tb,Dy,Ho,Er,Tm,Yb, Lu,Sc,Y,La and Ca D is a secondary dopant chosen from the group consisting of Pr,Sm,Eu,Tb,Fe,Co and Ni, M ~ D, M is present in an amount mole fraction y, sufficient to increase the ionic conductivity of the composition, D is present in an amount, mole fraction z, sufficient to decrease the electronic conductivity of the composition under reducing conditions, and about .
o.oS < d < about 0.30.
The composition of the present invention provides high ionic conductivity and low electronic conductivity under reducing conditions.
A fuel cell is disclosed. The ~uel cell . comprises an anode, a cathode, and a solid electrolyte .
: 20 between the anode and cathode, wherein the solid electrolyte comprises the composition described above.
A process for generating electricity is also disclosed. The process comprises providing a fuel cell, wherein the fuel cell comprises the fuel cell described above, supplying a fuel to the anode of the . fuel-cell, supplying an oxidant to the cathode side of the fuel cell, and electrochemically reacting the fuel - and the oxidant to prov.ide an electrical current.
....
.~ Brief Description of the Drawings ;- -~30 Figure:1 shows a.cross-sectional view of-a-fuel -,cell.. of *he;present invention~
.Figure 2.shows a plot of:log-total conductivity . as a function of oxygen partial pressure;
~! .
2071~88 WO9lt09430 PCr/US90/07075 ~:
Figure 3 shows a plot of electronic conductivity vs. secondary dopant level for a number of electrolyte compositions;
Figure 4 shows a plot of electrolytic domain boundary vs. secondary dopant level for a number of electrolyte compositions;
Figure S shows a plot of fuel cell voltage and electronic short circuit current vs. current density for two electrolyte compositions;
Figure 6 shows a plot of cell efficiency and power density vs. current density for two electrolyte compositions.
Description of the Preferred Embodiment ;~
The ceria electrolyte composition of the prasent invention comprises:
X y Z02-wherein:
M is a primary dopant chosen from the group consisting of Pr,Nd,Pm,Sm,Eu,Gd,Tb,Dy,Ho, Er,Tm,Yb,Lu,Sc,Y,La and Ca, D is a secondary dopant chosen from the group consisting of Pr,Sm,Eu,Tb,Fe,Co and Ni, M ~ D, and x, y, z and 2-d are coefficients denoting the atomic fractions-of the respective components and fall within the ranges set out below.
The primary dopant is chosen-to increase the ionic conductivity of the electrolyte relative to ceria compositions lacking the primary dopant.
Suitable primary dopants are-known~in the~art.
Preferably, the primary dopant, M,-is chosen from-the group co~sisting of Gd, Y, Ca, Sm, La, Nd and Sc.
More pr~ferably, M comprises Gd, Sm, Ca or Y. Most preferably, ~ comprises Gd.
SUBSTITUIE SHEE~
..~ , . .. . . .
, . ~., . .. ; ~ .. . .
207 1~8~
The secondary dopant, D, is chosen to decrease the electronic conductivity of the electrolyte composition under reducing conditions, relative to the electronic conductivity of ceria compositions lacking the secondary dopant. Suitable secondary dopants, D, comprise elements which reduce more easily than Ce.
Preferably, the secondary dopant has an ionic radius similar to that of Ce. Most preferably, D comprises Pr or Sm.
Specific examples of the composition of the present invention include:
cexGdyprzo2-dl CexGdysmzo2-d ' CexGdyEuzo2-d ' CexGdyTbzo2-d ~ ' .
cexGdyFez02-d ' CexGdycozo2-d ' CexGdyNizo2-d ' cexYyPrz02_ CexYySmz02 d~
CexYyEUz02_d ~ -- -. . . . ..
cexyyTbzo2-d ~ ., cexyyFezo2-d ' SUBSTITUTE SHET
.. , , ., , .. , , " . . . . . .. . . . . . .... . ....
.. ... .. . ... ..
. .
, , . ~, . ` -. ` , . . . .
.
i . , , ~ . ~ ` . . ` . . . .
- ........ ~ .. . . . . . .. . .
~071:~`8 W091~09430 PCT/US90/0707~ .
CexYycozo2-dl CexYyNiz02 d' CexCayPrzo2-d ' , Cexca 5CexCayEuzo2-dl ; x y z 2-d' ;
Ce Ca Fe o excaycz2-d ~ , ,, .
'i' .:
10Cexsmyprzo2-d : CexSmyEUz2_dl cexsmy~bzo2-d ' myFezo2 d' .~ Ce Sm Co d' ~; 15~ and CexSmyNizO2 d wherein x,y,z and d are within the ranges set out below.
: : The atomic fraction of Ce,. x, is within the range of about 0.7 to about O.9 and preferably falls within the range of about 0.75 to about 0.85.
The atomic fractions of the primary dopant, y, and the atomic fraction of the secondary dopant, z, are~chosen to the maximize ionic conductance of the SU8S~I~UTE SHE~
" .. . " . . ; . . , ;. .. ... .. . - . ;, ,.. .. ,. . -, . . . . . .
:.!,, . . .. . '. . " , :,', .,-,' ',' ", ,, . ,. ,'.. '.. ' ' . ' . ' ' 2071~8~
WO9t/09430 electrolyte and minimize the electronic conductance of the electrolyte under reducing conditions. The atomic fraction of primary dopant in the present composition, :
y, is preferably within the range of about 0.1 to about 0.3 and most preferably falls within the range from about 0.15 to about 0.25. The atomic fraction of secondary dopant in the present composition, z, is preferably within the range of about 0.001 to about 0.1 and most preferably falls within the range of about 0.01 to about 0.05. -~
The atomic fraction of oxygen in the present composition, 2-d, varies with the oxidation states of the primary and secondary dopants, with atomic fractions y and z and with oxygen partial pressure.
An oxygen vacancy is formed for each divalent dopant atom, one half of an oxygen vacancy is formed or each trivalent dopant atom and no o~ygen vacancy is formed for each quàdravalent dopant atom. The atomic fraction of oxygen in the composition of the present invention typically ranges from about 1.7 to ~bout 1.95 and most typically ranges from about 1.89S to about 1.9. Values for d may therefore typically range from 0.05 to about 0.30 and most typically range from 0.1 t~ 0.105.
The ceria electrolyte of the present invention may be made by conventional solid.state techniques.
.Inorganic precursor..materials are mixed and reacted to form a product of the desired composition. Precursor materials comprise compounds which decompose under suitable conditions to yield reactants which are then ' reacted to form the ceria.electrolyte.:product. The : relative amount of each precursor material in`the mixture is chosen to provide a-product ha~ing th~-desired ~olar composition.
~ 35 In a preferred process, stoichiometric amounts of water soluble inorganic precursor materials are UIE SH~I ' .
-. , . --- . -- - - - . ........ ... . . . - . .
. ~ . . . .
207~88 -PCI`/US90/0707s ':
combined to form an aqueous solution. Reactants are .
precipitated from the solution. The precipitate is filtered, dried and ground to form a fine powder. The ~;
powder is then calcined in air. The calcined powder is pressed and sintered to form the ceria electrolyte ;-composition.
The ceria electrolyte of the present invention is used as the electrolyte in a solid electrolyte fuel cell. A solid electrolyte fuel cell of the present invention is shown in Figure l and comprises an anode 2, a cathode 4 and a ceria electrolyte 6 of the -present invention between the anode 2 and cathode 4, an external circuit 8 electrically conne~ting the anode 2 and the cathode 4, a first flow field 10 having passages 12 for directing reactants to and reaction products away from the anode 2, and a second flow field 14 having passages 16 for directing reactants to and reaction products from the cathode 4.
The fuel cell is operated at pressures between 1 and 10 atm and temperatures between 600-C - lOOO-C to generate an electrical current by electrochemically reacting the fuel and oxidant streams. Key fuel cell performance parameters include current density, cell voltage, and power density and cell efficiency.
Current density is defined as the current generated per-unit cross sectional area of the electrolyte expressed in milliamps/square centimeter (mA/cm2). Cell voltage is defined as the voltage generated by the cell expressed in volts--(V)-. Power density is defined as the power generated per unit-cross sectional area of the~electrolyte,~ expressed as - watts/square centimeter (w/cm2). Cell efficiency is defined as DC power produced/standard enthalpy of fuel electrochemically converted. ~-The electrolyte composition of the present invention provides high ionic conductance but exhibits SUt~ST~TUTE SHE~T
..... . ... ... . ... . . . .... . ..... .. .. .. ... . .. . ... . . .. . ... .
.,.. ,... : . . . - . : , .. , ~ .
.
- . .
- -' ' ' .
, ~ . ' , ~ , .
2071888 ::
PCI`/US90/0707s g _ .-low electronic conductivity at low 2 partial pressures. Preferably, the electrolyte of the present invention exhibits an electrolytic conductivity of less than about 0.3 S/cm at an 2 partial pressure of about 1 X 10 23 atm. The behavior of the electrode of the present invention with regard to 0 2 partial pressure may be characterized by reference to an electrolytic domain boundary value. The electrolytic domain boundary is defined as the 2 partial pressure at which the electronic conductivity of the electrolyte equals the ionic conductivity of the electrolyte. Preferably, the electrolyte of the present invention exhibits an electrolytic domain boundary of less than about 5 X 10 19 atm 2 at 700 C.
Most preferably, the electrolyte of the present invention exhibits an electrolytic domain boundary of ;
less than about 5 X 10 20 atm 2 at 700C. T~e low electrolytic domain boundary of the electrolyte provides performance advantages to fuel cells in which the electrolyte is employed. Since the electrolyte of the present invention provides low electronic conductivity and high ionic conductivity at low 2 partial pressures, short circuiting across the electrolyte is reduced. Power and efficiency losses which result from short circuiting are correspondingly reduced.
The basis for the electronic conductivity of a conve~tional ceria electrolyte appears to be a -`
departure from stoichiome~ry in the ceria as it is reduced under low 2 partial pressures.
The reaction may-be expressed as~
oO - VO ~ 2e + 1/2 2(gas)~' ~~
where~
" .. . . . . . . . .
0O is an oxygen site in the ceria electrolyte, ~! 35 and ,, .
",.
SU~STITllTE SHEET
- ' . " ' ' ' . ~ . ' . ' ' ' ' .
2~71~88 ~
W091/Og430 PC~/~S90/07075 V0 is a vacant positively charged site in the ceria electrolyte.
Reduction converts an oxygen to a vacant site plus two free electrons. Movement of the free electrons through the electrolyte provides the mechanism for internal short circuiting of the electrolyte.
While not wishing to be bound by any particular theory, it is believed that the secondary dopant, D, ;
of the composition of the present invention minimizes the electronic conductivity of the composition by trapping electrons, i.e. by reducing the net total of mobile electrons in the composition.
52.11 grams Ce(N03)3 6H20, 10.56 grams Gd(N03)2 and 0.65 grams Pr(N03) were combined, dissolved in distilled water and diluted to form a 0.3M nitrate solution. The nitrate solution was added dropwise to a bath o~ 0.3M ammonium oxalate to precipitate the Ce, Gd and Pr reactants. Additions of 10~ N~40H were made to maintain the pH between 6.5 and 7Ø After all the nitrate solution had been added to the bath, additional NH40H is added to raise the pH of the solution to 7.5 to ensure complete precipitation. The precipitate was filtered, oven dried at 140-C and crushed in a porcelain mortar and pestle to form a fine powder. The powder was calcined in an alumina crucible-in air at 750-C for 16 hours. The calcined powder was mixed with 0.3 wt % polyvinyl alcohol as a binder. The mixture was pressed at 200MPa, crushed, reground and finally repressed at 400MPa to form wafers. The wafers were sintered at temperatures ~etween 1300-C and 1525-~ to form wafers having a nominal composition of CeO ~Gdo 19PrO 012 d SUBSTITUTE SHEET
.. i.......... . . . ~......... ~ . . .
. . .
~ . . . . . . .. . . . . .
; ~ , . - - . .
. . . -. , ., ~ , . .
2`07~88 Wafers havi~g a nominal composition:
ceO 8Gdo~ 22-d were also prepared by a process analogous to the : ;
process described above.
Conductivity measurements were made using the A.C. impedence technique. Figure 2 shows total -~
conductivity (S/cm) of each composition as a function.
f 2 partial pressure (atm) at 700C. The electrolytic domain boundary of the CeO 8Gdo 2l 9 composition was about 8 X 10 19 atm 2' The electrolytic domain boundary of the 0.8 0.lsPro.olo2-d composition was 4.6 X 1o~
atm 2' Wafers having nominal compositions:
ceO.8GdO.2_zPrz02_d and ceO 8Gdo2-zSmz2-d where: 0 < z < 0.06 and 0.07 < d < 0.1 , were prepared by processes analogous to the process described in Example 1.
Figure 3 shows a plot of electronic conductivity under reducing conditions (Po2 = 1 x 10 23 atm) versus atomic ;fraction of secondary dopant for the above described wafers at 700C-. ; . .
With regard to the CeO 8Gdo 2_zPrz02_ compositions, the electronic conductivity reaches a , . . ,; . .. .. . ... ..... . . . . . .
minimum of about 0.18 S/cm at a mole fraction Pr of about 0.010. The results obtained using Sm as a ~;
` SUBSTITU~E SHEI
2071~8 WO91/09430 PCT/US90/07075 `
secondary dopant were in agreement with those obtained ;
using Pr as the secondary dopant.
Figure 4 shows a plot of electronic domain boundary (atm 2) vexsus atomic fraction of secondary ,' 5 dopant for the above described wafers at 700-C. The electronic domain boundary of the Ce~ 8Gd2 XPrx02 d compositions, fell below about 5XlO atm for atomic fractions of Pr of greater than about 0.001. The results obtained using Sm as the secondary dopant were in agreement with those using Pr as the secondary dopant.
The conductivity data collected in Example I were used to calculate the performance of fuel cells using each of the electrolyte compositions. The calculations were based on a fuel cell having a 0.005 inch thick electrolyte layer operated at 710'C with negligible electrode losses. The method of calculation is conventional in the art, e.g. see generally, P.N. Ross, Jr. and T . G . Benjamin, "Thermal Efficiency of Solid Electrolyte Fuel Cells with Mixed Conduction", Journal of Power Sources 1 (1976/77) 311-321.
Figure 5 shows a plot of calculated cell voltage and calculated electronic short circuit current versus current density`-at 710-C. A fuel cell having an electrolyte of the present invention exhibits an 'electronic short circuit current that is substantially lower than the short circuit current exhibited by fuel cell ha~ing a CeO BGdo 22-d ëlectrolyte at current densities l~ss than 2000 ma/cm . '' Figure 6 shows a plot`'of calculatéd celi efficiency and-calculated power density versus current density at'710-C. A fuel cell having an electrolyte composition of the present invention exhibits a maximum cell efficiency of about 0.48 at a SUBSTITUTE SHET
... , . . . . . , . . , , . . .. ., ., ,, . .. , ~ . ., . , .. , . ",, . .,,,,, . ,,, . , .. , . .. ~ . .. .. ... . . . . .. .. .....
~ ' ' , ' ,, ' ., , : , ' ,' ' ,, ~ 1~ , ,~, ' ' . , 2 0 7 ~
WOgl/09430 PCT/US90/07075 current density of about 750A/cm2, while a cell having a CeO 8Gdo 22 d electrolyte exhibits a maximum cell efficiency of about 0.4 at a current density of about 1000 mA/cm2.
A fuel cell having an electrolyte of the present invention exhibits a maximum power density of about 1.2 w/cm2 at a current density of about 2400 mA/cm2 at 710-C, while a fuel cell having CeO 8Gdo 22 d electrolyte exhibits a maximum power density of about 0.9 w/cm2 at a current density of about 2000 mA/cm2 at 710-C.
The electrolyte composition of the present invention provides high ionic conductivity and reduced electronic conductivity under low oxygen partial pressures. Fuel cells employing the electrolyte composition of the present invention will exhibit improved efficiency and higher power density relative to fuel cells employing conventional ceria electrolyte compositions, due to a reduction in hort circuiting between the electrodes of the fuel cell.
While preferred embodiments have been shown and described, various modifications and substitutions may be made thereto without departing from the spirit and scope of the invention. Accordingly, it is to be understood that the present invention has been described by way of illustrations and not limitation.
What is claimed is:
,. .. ..
, ~ - SU5STITUTE SHET
.,.. , ' ~ , . ~.
., :
~ ' : ' . ' ;~\
.
Claims (16)
1. An electrolyte composition, comprising:
CeXMyDzO2-d' wherein:
M is chosen from the group consisting of Pr,Nd,Pm,Sm,Eu,Gd,Tb,Dy,HO,Er,Tm,Yb,Lu,Sc,Y,La and Ca, D is chosen from the group consisting of Pr,Sm,Eu,Tb,Fe,Co and Ni, M D, M is present in an amount, mole fraction y, effective to increase the ionic conductivity of the composition, D is present in an amount, mole fraction z, effective to decrease the electronic conductivity of the composition under reducing conditions, and about 0.05 ? d ? about 0.30.
CeXMyDzO2-d' wherein:
M is chosen from the group consisting of Pr,Nd,Pm,Sm,Eu,Gd,Tb,Dy,HO,Er,Tm,Yb,Lu,Sc,Y,La and Ca, D is chosen from the group consisting of Pr,Sm,Eu,Tb,Fe,Co and Ni, M D, M is present in an amount, mole fraction y, effective to increase the ionic conductivity of the composition, D is present in an amount, mole fraction z, effective to decrease the electronic conductivity of the composition under reducing conditions, and about 0.05 ? d ? about 0.30.
2. The composition of claim 1, wherein the composition exhibits an electrolytic domain boundary of less than 3 X 10-19 atm 02 at about 700°C.
3. The composition of claim 1, wherein the composition exhibits an electronic conductivity of less than 0.8 S/cm at an oxygen partial pressure of less than 3 X 10-19 atm 02 at about 700°C.
4. The composition of claim 1, wherein:
M is chosen from the group consisting of Gd,Y,Ca,Sm,La,Nd and Sc.
M is chosen from the group consisting of Gd,Y,Ca,Sm,La,Nd and Sc.
5. The composition of claim 4, wherein:
M is chosen from the group consisting of Gd,Sm,Ca and D is chosen from the group consisting of Pr and Sm.
M is chosen from the group consisting of Gd,Sm,Ca and D is chosen from the group consisting of Pr and Sm.
6. The composition of claim 1, wherein:
about 0.7 ? x ? about 0.9, about 0.1 ? y ? about 0.3, about 0.001 ? z ? about 0.1, and about 0.1 ? d ? about 0.30.
about 0.7 ? x ? about 0.9, about 0.1 ? y ? about 0.3, about 0.001 ? z ? about 0.1, and about 0.1 ? d ? about 0.30.
7. The composition of claim 6, wherein:
about 0.75 ? x ? about 0.85, about 0.15 ? y ? about 0.25, and about 0.01 ? z ? about 0.05.
about 0.75 ? x ? about 0.85, about 0.15 ? y ? about 0.25, and about 0.01 ? z ? about 0.05.
8. A fuel cell, comprising:
an anode;
a cathode; and a solid electrolyte between the anode and the cathode, said electrolyte comprising:
CeXmyDz02-d, wherein:
M is chosen from the group consisting of Pr,Nd,Pm,Sm,Eu,Gd,Tb,Dy,Ho,Er,Tm,Yb,Lu,Sc,Y,La and Ca, D is chosen from the group consisting of Pr,Sm,Eu,Tb,Fe,Co and Ni, M ? D, M is present in an.amount, mole fraction y, effective to increase the ionic conductivity of the composition, D is present in an amount, mole fraction z, effective to decrease the electronic conductivity of the composition under reducing conditions, and about 0.05 ? d ? about 0.30.
an anode;
a cathode; and a solid electrolyte between the anode and the cathode, said electrolyte comprising:
CeXmyDz02-d, wherein:
M is chosen from the group consisting of Pr,Nd,Pm,Sm,Eu,Gd,Tb,Dy,Ho,Er,Tm,Yb,Lu,Sc,Y,La and Ca, D is chosen from the group consisting of Pr,Sm,Eu,Tb,Fe,Co and Ni, M ? D, M is present in an.amount, mole fraction y, effective to increase the ionic conductivity of the composition, D is present in an amount, mole fraction z, effective to decrease the electronic conductivity of the composition under reducing conditions, and about 0.05 ? d ? about 0.30.
9. The fuel cell of claim 8, wherein the fuel cell exhibits improved power density and efficiency.
10. The fuel cell of claim 9, wherein:
M is chosen from the group consisting of Gd,Y,Ca,Sm,Th,La,Nd and Sc.
M is chosen from the group consisting of Gd,Y,Ca,Sm,Th,La,Nd and Sc.
11. The fuel cell of claim 8, wherein:
M is chosen from the group consisting of Gd,Sm,Ca and Y and D is chosen from the group consisting of Pr and Sm.
M is chosen from the group consisting of Gd,Sm,Ca and Y and D is chosen from the group consisting of Pr and Sm.
12. The fuel cell of claim 8, wherein:
about 0.7 < x < about 0.9, about 0.1 < y > about 0.3, about 0.01 ~ z < about 0.1, and about 0.1 ~ d < about 0.30.
about 0.7 < x < about 0.9, about 0.1 < y > about 0.3, about 0.01 ~ z < about 0.1, and about 0.1 ~ d < about 0.30.
13. A method for generating electricity, comprising:
providing a fuel cell, said fuel cell comprising:
an anode;
a cathode; and a solid electrolyte between the anode and the cathode, said electrolyte comprising:
CeXmyDz02-d' wherein:
M is chosen from the group consisting of Pr,Nd,Pm,Sm,Eu,Gd,Tb,Dy,Ho,Er,Tm,Yb,Lu,Sc,Y,La and Ca, D is chosen from the group consisting of Pr,Sm,Eu,Tb,Fe,Co.and Ni, M ? D, M is present in an amount, mole fraction y, effective to increase the ionic conductivity of the composition, D is present in an amount, mole fraction z, effective to decrease the electronic conductivity of the composition under reducing conditions, and about 0.05 ? d ?, about 0.30;
supplying a fuel gas to the anode;
supplying an oxidant gas to the cathode; and electrochemically reacting the fuel gas and the oxidant gas in the fuel cell at a temperature between about 600°C and about 1000°C and a pressure between about 1 atm and 10 atm to produce electricity.
providing a fuel cell, said fuel cell comprising:
an anode;
a cathode; and a solid electrolyte between the anode and the cathode, said electrolyte comprising:
CeXmyDz02-d' wherein:
M is chosen from the group consisting of Pr,Nd,Pm,Sm,Eu,Gd,Tb,Dy,Ho,Er,Tm,Yb,Lu,Sc,Y,La and Ca, D is chosen from the group consisting of Pr,Sm,Eu,Tb,Fe,Co.and Ni, M ? D, M is present in an amount, mole fraction y, effective to increase the ionic conductivity of the composition, D is present in an amount, mole fraction z, effective to decrease the electronic conductivity of the composition under reducing conditions, and about 0.05 ? d ?, about 0.30;
supplying a fuel gas to the anode;
supplying an oxidant gas to the cathode; and electrochemically reacting the fuel gas and the oxidant gas in the fuel cell at a temperature between about 600°C and about 1000°C and a pressure between about 1 atm and 10 atm to produce electricity.
14. The method of claim 13, wherein:
M is chosen from the group consisting of Gd,Y,Ca,Sm,Th,La,Nd and Sc.
M is chosen from the group consisting of Gd,Y,Ca,Sm,Th,La,Nd and Sc.
15. The method of claim 13, wherein:
M is chosen from the group consisting of Gd,Sm,Ca and Y, and D is chosen from the group consisting of Pr and Sm.
M is chosen from the group consisting of Gd,Sm,Ca and Y, and D is chosen from the group consisting of Pr and Sm.
16. The method of claim 13, wherein:
about 0.7 ? x ? about 0.9, about 0.1 ? y ? about 0.3, about 0.001 ? z ? about 0.1, and about 0.1 ? d ? about 0.30.
about 0.7 ? x ? about 0.9, about 0.1 ? y ? about 0.3, about 0.001 ? z ? about 0.1, and about 0.1 ? d ? about 0.30.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US450,420 | 1989-12-14 | ||
| US07/450,420 US5001021A (en) | 1989-12-14 | 1989-12-14 | Ceria electrolyte composition |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2071888A1 true CA2071888A1 (en) | 1991-06-15 |
Family
ID=23788026
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002071888A Abandoned CA2071888A1 (en) | 1989-12-14 | 1990-12-04 | Ceria electrolyte composition |
Country Status (6)
| Country | Link |
|---|---|
| US (1) | US5001021A (en) |
| EP (1) | EP0504260B1 (en) |
| JP (1) | JPH05503804A (en) |
| CA (1) | CA2071888A1 (en) |
| DE (1) | DE69020360T2 (en) |
| WO (1) | WO1991009430A2 (en) |
Families Citing this family (23)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE4238688A1 (en) * | 1992-11-17 | 1994-05-19 | Bosch Gmbh Robert | Sintered solid electrolyte with high oxygen ion conductivity |
| US5665482A (en) * | 1995-01-10 | 1997-09-09 | Tosoh Corporation | Fluorite structure type ceria type solid electrolyte |
| US5725965A (en) * | 1995-04-25 | 1998-03-10 | Gas Research Institute | Stable high conductivity functionally gradient compositionally layered solid state electrolytes and membranes |
| KR0165651B1 (en) * | 1995-09-28 | 1999-03-30 | 모리시타 요이치 | Electrochemical device |
| US6117582A (en) * | 1995-11-16 | 2000-09-12 | The Dow Chemical Company | Cathode composition for solid oxide fuel cell |
| US5993986A (en) * | 1995-11-16 | 1999-11-30 | The Dow Chemical Company | Solide oxide fuel cell stack with composite electrodes and method for making |
| US5670270A (en) * | 1995-11-16 | 1997-09-23 | The Dow Chemical Company | Electrode structure for solid state electrochemical devices |
| US5759936A (en) * | 1996-03-21 | 1998-06-02 | Haldor Topsoe As | Lanthanide ceramic material |
| US6228520B1 (en) | 1997-04-10 | 2001-05-08 | The Dow Chemical Company | Consinterable ceramic interconnect for solid oxide fuel cells |
| US5935727A (en) * | 1997-04-10 | 1999-08-10 | The Dow Chemical Company | Solid oxide fuel cells |
| US5922486A (en) * | 1997-05-29 | 1999-07-13 | The Dow Chemical Company | Cosintering of multilayer stacks of solid oxide fuel cells |
| EP0947487A1 (en) * | 1998-03-31 | 1999-10-06 | Haldor Topsoe A/S | Fluorite ceramic material |
| ATE228982T1 (en) | 1998-11-13 | 2002-12-15 | Eidgenoess Tech Hochschule | METHOD FOR PRODUCING DOPED CEROXIDE CERAMICS |
| US6770392B2 (en) | 2001-04-27 | 2004-08-03 | Air Products And Chemicals, Inc. | Ceria based solid electrolytes |
| RU2236722C1 (en) * | 2003-06-10 | 2004-09-20 | Мятиев Ата Атаевич | Electrode-electrolyte pair on base of cerium dioxide (variants), method for making it (variants) and organogel |
| JP2005116478A (en) * | 2003-10-10 | 2005-04-28 | National Institute Of Advanced Industrial & Technology | Oxygen ion-permeable membrane structure body |
| US20060127726A1 (en) * | 2004-12-14 | 2006-06-15 | Feng-Yun Wang | Solid electrolyte based on magnesia-doped ceria |
| WO2007027144A1 (en) * | 2005-08-31 | 2007-03-08 | David Andersson | Doped ceria ion conductor |
| US7645535B2 (en) * | 2005-11-14 | 2010-01-12 | General Electric Company | Method and materials for bonding electrodes to interconnect layers in solid oxide fuel cell stacks |
| KR101110850B1 (en) | 2009-07-22 | 2012-02-16 | 연세대학교 산학협력단 | Electronic Conductivity Control In SOFC Electrolyte Of SOFC By Oxygen Partial Pressure In Anode And Working Method Thereof |
| JP2011213588A (en) * | 2010-03-31 | 2011-10-27 | Toyota Motor Corp | High ion-conductive solid electrolyte |
| CN102201589B (en) * | 2011-04-14 | 2013-04-24 | 黑龙江大学 | Preparation method of nano electrolyte material for mesothermal solid oxide fuel cell |
| AU2022381461A1 (en) * | 2021-11-08 | 2024-05-02 | Rhodia Operations | Cerium-gadolinium composite oxide |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5426690B1 (en) * | 1969-10-27 | 1979-09-05 | ||
| EP0275356B1 (en) * | 1984-10-23 | 1991-06-05 | Mitsubishi Jukogyo Kabushiki Kaisha | Solid electrolyte fuel cell and method for preparing it |
| FR2583053B1 (en) * | 1985-06-07 | 1987-12-24 | Rhone Poulenc Spec Chim | PIGMENTS BASED ON CERIUM AND PRASEODYM, THEIR PREPARATION PROCESS AND THEIR APPLICATIONS |
| US4702971A (en) * | 1986-05-28 | 1987-10-27 | Westinghouse Electric Corp. | Sulfur tolerant composite cermet electrodes for solid oxide electrochemical cells |
| US4851303A (en) * | 1986-11-26 | 1989-07-25 | Sri-International | Solid compositions for fuel cells, sensors and catalysts |
-
1989
- 1989-12-14 US US07/450,420 patent/US5001021A/en not_active Expired - Lifetime
-
1990
- 1990-12-04 EP EP91901142A patent/EP0504260B1/en not_active Expired - Lifetime
- 1990-12-04 DE DE69020360T patent/DE69020360T2/en not_active Expired - Fee Related
- 1990-12-04 WO PCT/US1990/007075 patent/WO1991009430A2/en active IP Right Grant
- 1990-12-04 CA CA002071888A patent/CA2071888A1/en not_active Abandoned
- 1990-12-04 JP JP3501585A patent/JPH05503804A/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| DE69020360T2 (en) | 1996-05-30 |
| WO1991009430A2 (en) | 1991-06-27 |
| JPH05503804A (en) | 1993-06-17 |
| WO1991009430A3 (en) | 1991-09-05 |
| US5001021A (en) | 1991-03-19 |
| EP0504260A1 (en) | 1992-09-23 |
| EP0504260B1 (en) | 1995-06-21 |
| DE69020360D1 (en) | 1995-07-27 |
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